CN116061629A - Automobile active suspension control method - Google Patents

Abstract

The invention discloses an automobile active suspension control method which comprises a sensing data acquisition unit, a road condition state sensing unit, a mode switching control unit, an expert data calibration unit, a closed-loop control force correction unit and an active suspension control unit. The sensing data acquisition unit is used for acquiring vehicle data; the road condition state sensing unit is used for judging the running conditions of the vehicle, including but not limited to bumpy road surfaces, ice and snow muddy road surfaces, ramp road surfaces, turning road surfaces and horizontal good road surfaces; the mode switching control unit is used for adopting different sensing modes according to different vehicle driving conditions, wherein the sensing modes comprise a strong sensing mode, a medium sensing mode and a weak sensing mode; the expert data calibration unit integrates an expert database through simulation, real vehicle calibration and experience analysis; the closed-loop correction force correction unit is used for constructing a closed-loop correction function so as to correct the active suspension control force; the active suspension control unit is used for controlling the chassis to lift and adjusting the posture of the vehicle body.

Description

Automobile active suspension control method

Technical Field

The invention relates to an active suspension control method of an automobile.

Background

At present, the intelligent degree of the vehicle is higher and higher, and unmanned automobiles gradually appear. When the ADAS function and the AD function of the unmanned automobile are developed, the development of related functions is mostly focused on the study of environmental perception, path planning and decision control, and the active suspension control technology under the unmanned condition is not considered, so that the automobile body level of the unmanned automobile when the unmanned automobile runs on different road conditions is effectively ensured, and the smoothness and the comfort of the automobile are improved, and the technical problem to be solved urgently by the applicant is solved. To improve these problems, the present invention proposes an active suspension control method for an automobile.

Disclosure of Invention

The invention aims to provide an active suspension control method for an automobile, which aims to solve the problems faced in the background art.

In order to achieve the above purpose, the present invention provides the following technical solutions: an automobile active suspension control method comprises a sensing data acquisition unit, a road condition sensing unit, a mode switching control unit, an expert data calibration unit, a closed-loop control force correction unit and an active suspension control unit.

The sensing data acquisition unit comprises a centroid side deflection angle sensor, a vehicle body side inclination angle sensor, a vehicle body vertical acceleration sensor, a vehicle body pitch angle sensor, a cab camera, a vehicle speed sensor, a vehicle body height sensor and a front wheel steering angle measuring system; the method is used for respectively obtaining a centroid side deflection angle, a vehicle body side inclination angle, a vehicle body vertical acceleration, a vehicle body pitch angle, a driver peripheral swing distance, a vehicle longitudinal speed, a suspension height change and a front wheel corner; according to the collected data, a bumping factor is designed for evaluating the comprehensive performance of the bumping degree of the bumpy road surface; introducing a turning factor for evaluating the rollover risk and the rollover degree of the automobile during turning;

The road condition sensing unit comprises a map, a navigation, a camera, a road condition database and a road condition monitor; the navigation and map is used for acquiring the current vehicle position; the camera is used for acquiring barriers, road gradient and ground concave-convex degree of the front side, the rear side and the lateral side of the vehicle; the road working condition database judges the road working conditions according to the current vehicle position, the obstacle, the road gradient, the ground concave-convex degree and the off-line road database, including but not limited to bumpy road surfaces, ice and snow muddy road surfaces, ramp road surfaces, turning road surfaces and horizontal good road surfaces; the road surface condition monitor comprises a front end acquisition signal core sensor, a host acquisition system, a wireless network and a server, and is used for monitoring the changes of real-time data such as road surface ponding, snow thickness, rain and snow quantity, dry and wet conditions and the like and obtaining road viscosity factors and road humidity coefficients; analyzing different ice, snow and muddy road conditions by a cluster analysis method, and setting an environment wet coefficient;

the mode switching control unit comprises a strong sensing mode, a medium sensing mode and a weak sensing mode, different sensing modes are adopted according to the conditions of different identified roads, and the quantity and the types of vehicle state parameters acquired by the different sensing modes are different;

The expert data calibration unit comprises the steps of selecting 100 different bumpy road conditions for a plurality of custom types of vehicles to simulate, calibrate and empirically analyze, so as to form active suspension control force output of the vehicles under different speeds and different road conditions, and integrating an expert database;

the closed-loop control force correction unit comprises a closed-loop correction function constructed by a centroid side deflection angle, a vehicle body side inclination angle, a vehicle body vertical acceleration and a vehicle body pitch angle which are acquired by the sensing data acquisition unit, so as to obtain correction forces of different self-defined vehicle types and further correct the active suspension control force;

the active suspension control unit comprises a pressure sensor, a height sensor, an air spring, a damping continuously adjustable shock absorber, an electromagnetic valve, an air pump, an air storage tank and an electronic control unit.

The road condition state sensing unit judges that the running road condition of the vehicle is a bumpy road surface;

when the working condition is bumpy road surface, the mode switching control unit adopts a strong sensing mode, and a centroid slip angle sensor in the sensing data acquisition unit acquires a centroid slip angle beta and a weight coefficient

The value range is 0 to 1,/for>

A smaller value means that the smaller the degree of cornering of the vehicle during movement, the better the steering stability, and +. >

When the centroid side deflection angle is 0 degrees; />

The larger means that the greater the degree of cornering of the vehicle during movement, the poorer the steering stability, and +.>

When the centroid side deflection angle is 90 degrees;

calculating a root mean square value of the centroid slip angle according to the following formula:

wherein: beta _t The centroid side deflection angle acquired at the moment t;

N ₁ the number of sampling the centroid slip angle is N ₁ ＝T/ns ₁ ；

T is a time period;

ns ₁ the signal acquisition period is the centroid side deflection angle signal;

the body roll angle sensor in the sensing data acquisition unit acquires the body roll angle

Weight coefficient

The value range is 0 to 1,/for>

Smaller means that the vehicle is less tilted during movement, the lower the probability of rollover of the vehicle,

when the roll angle of the vehicle body is 0 degree; />

A larger value indicates a larger degree of roll of the vehicle during movement, and a higher probability of rollover of the vehicle is +.>

When the roll angle of the vehicle body is 90 degrees;

the root mean square value of the roll angle of the vehicle body is calculated according to the following formula:

wherein:

the roll angle of the vehicle body is acquired at the moment t;

N ₂ the number of the sampled roll angles of the vehicle body is N ₂ ＝T/ns ₂ ；

T is a time period;

ns ₂ the method comprises the steps of acquiring a vehicle body roll angle signal;

the vehicle body vertical acceleration sensor in the sensing data acquisition unit acquires vehicle body vertical acceleration a _z Weight coefficient

The value range is 0 to 1,/for>

The smaller the vertical vibration of the vehicle in the moving process is, the lower the probability that the wheels are separated from the ground is, the better the riding comfort is, and the more>

When the vehicle does not vibrate vertically; />

The larger the vertical vibration of the vehicle in the moving process is, the higher the probability that the wheels are separated from the ground is, the worse the riding comfort is, and the more the vehicle is>

Indicating that the wheel is separated from the ground;

the root mean square value of the vertical acceleration of the vehicle body is calculated according to the following formula:

wherein: a, a _zt The vertical acceleration of the vehicle body is acquired at the moment t;

N ₃ the number of samples of the vertical acceleration of the vehicle body is N ₃ ＝T/ns ₃ ；

T is a time period;

ns ₃ the method is characterized in that the method is a vehicle body vertical acceleration signal acquisition period;

the vehicle body pitch angle sensor in the sensing data acquisition unit acquires a vehicle body pitch angle theta and a weight coefficient

The value range is 0 to 1,/for>

Smaller means that the pitch degree of the vehicle is smaller during movement, and the front and rear suspensions of the vehicleThe height difference is small, and the head is added>

0 represents that the vehicle is running smoothly; />

The larger the pitch degree of the vehicle in the moving process, the larger the height difference between front and rear suspensions of the vehicle, and the greater the +.>

The time indicates that the vehicle turns upward or turns downward;

calculating the root mean square value of the pitch angle of the vehicle body according to the following formula:

wherein: θ _t The pitch angle of the vehicle body is acquired at the moment t;

N ₄ The pitch angle of the vehicle body is sampled by the number N ₄ ＝T/ns ₄ ；

T is a time period;

ns ₄ the pitch angle signal acquisition period of the vehicle body;

the cab camera in the sensing data acquisition unit acquires a driver pendulum distance s and a pendulum weight coefficient

The value range is 0 to 1, when a driver drives on a bumpy road, the driver can shake in the front, back, left and right directions due to the bumpy road, and the smaller the shaking amplitude is, the smaller the circumferential distance is, and the smaller the influence of the bumpy road on the driver is; the larger the swing amplitude is, the larger the swing distance is, and the larger the influence of road jolting on a driver is;

the root mean square value of the driver's turn distance is calculated according to the following formula:

wherein: s is(s) _t The driver circle swing distance acquired at the time t;

N ₅ sampling the number of the driver circle swing distances, N ₅ ＝T/ns ₅ ；

T is a time period;

ns ₅ the method comprises the steps of (1) setting a distance signal acquisition period for a driver;

designing a comprehensive performance index function for evaluating the bumping degree of a bumpy road surface:

the conversion into matrix form is as follows: />

Wherein ρ is a jolt factor, Q _e Correcting the matrix for the parameter weight, wherein

Is 1 x 1 gaussian white noise.

Because the performance requirements on different vehicle types are different under the same road surface, the vehicle types are customized to be divided into A-type vehicles, B-type vehicles and C-type vehicles according to the different vehicle types, wherein the A-type vehicles are small vehicles with the wheelbase of less than 2700mm, the B-type vehicles are medium-sized vehicles with the wheelbase of between 2700 and 2850mm, and the C-type vehicles are large vehicles with the wheelbase of more than 2850 mm; hereinafter, i-type vehicle, wherein i takes a value of A, B, C;

For type A vehicles, the preset pitch factor range is [ ρ ] _Amin ,ρ _Amax ]When ρ < ρ _Amin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Amin ≤ρ≤ρ _Amax At the time of vehicle speedWhen the speed is lower than 65km/h, the vehicle is judged to be in a bump low risk zone, when the speed is higher than 65km/h and lower than 70km/h, the vehicle is judged to be in a bump medium risk zone, and when the speed is higher than 70km/h, the vehicle is judged to be in a bump high risk zone; when ρ > ρ _Amax When the vehicle is judged to be in a bumpy high risk interval;

for type B vehicles, the preset pitch factor range is [ ρ ] _Bmin ,ρ _Bmax ]When ρ < ρ _Bmin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Bmin ≤ρ≤ρ _Bmax When the vehicle speed is lower than 55km/h, the vehicle is judged to be in a bumpy low risk interval, when the vehicle speed is higher than 55km/h and lower than 60km/h, the vehicle is judged to be in a bumpy medium risk interval, and when the vehicle speed is higher than 60km/h, the vehicle is judged to be in a bumpy high risk interval; when ρ > ρ _Bmax When the vehicle is judged to be in a bumpy high risk interval;

for a C-type vehicle, the preset bump factor range is [ ρ ] _Cmin ,ρ _Cmax ]When ρ < ρ _Cmin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Cmin ≤ρ≤ρ _Cmax When the vehicle speed is lower than 45km/h, the vehicle is judged to be in a bumpy low risk zone, when the vehicle speed is higher than 45km/h and lower than 50km/h, the vehicle is judged to be in a bumpy medium risk zone, and when the vehicle speed is higher than 50km/h, the vehicle is judged to be in a bumpy high risk zone; when ρ > ρ _Cmax When the vehicle is judged to be in the bump high risk section.

The expert data calibration unit comprises the following steps:

step 1: selecting 100 different bumpy road conditions for different types of vehicles, performing simulation, real vehicle calibration and experience analysis to form an i-type vehicle active suspension control force output under different vehicle speeds and different road conditions, and forming an expert database;

step 2: according to the fact that the vehicles of different vehicle types are in different bumpy risk intervals and different vehicle speeds, the expert database can be compared to obtain that the active suspension control force required by the four wheels on the left side and the right side of the i-type vehicle is [ F ] _iFL F _iFR F _iRL F _iRR ]；

Wherein F is _iFL Active suspension control force for left front wheel of i-type vehicle, F _iFR Active suspension control force for right front wheel of i-type vehicle, F _iRL Active suspension control force for left rear wheel of i-type vehicle, F _iRR The control force is actively controlled by the suspension of the right rear wheel of the i-type vehicle.

The closed-loop control force correction unit is used for correcting the four wheel active suspension control forces in the scheme; for the roll angle beta and the roll angle of the vehicle body according to the mass center

Vertical acceleration a of vehicle body _z Constructing an i-type vehicle closed loop correction function by using a vehicle body pitch angle theta>

Calculating the i-type vehicle closed loop correction force F _ib ＝k _i f _i Wherein k is _i The closed loop correction function coefficient of the i-type vehicle is restricted to 0 < k _i Is less than or equal to 1; optimal active suspension control force output of i-type vehicle: />

Wherein F is _iZFL Outputting control force for optimal active suspension of left front wheel of i-type vehicle, F _iZFR Outputting control force for optimal active suspension of right front wheel of i-type vehicle, F _iZRL Outputting control force for the optimal active suspension of the left rear wheel of the i-type vehicle, F _iZRR Outputting control force for the optimal active suspension of the right rear wheel of the i-type vehicle;

the electronic control unit in the active suspension control unit receives the optimal active suspension output control force of four wheels, realizes the adjustment of the vehicle body posture by adjusting the opening and closing of electromagnetic valves to realize the inflation and deflation of the air spring and the damping of the damping continuously adjustable shock absorber, and adjusts the rigidity of the air spring of the active suspension and the damping of the damping continuously adjustable shock absorber by utilizing proportional-integral-differential closed loop feedback control.

The road condition state sensing unit judges that the running road condition of the vehicle is ice, snow and muddy road;

the ice and snow muddy road surface comprises the following steps:

step 1: when the working condition is ice and snow muddy road, the mode switching control unit adopts a strong sensing mode to perform clustering analysis on relevant parameters of the ice and snow muddy road working condition, and the specific steps are as follows:

step 1.1: setting n sample objects, using x ₁ ,x ₂ ,…,x _n A representation; multi-period data acquisition is carried out during vehicle driving, and each sample object comprises m data indexes x _i1 ,x _i2 ,…,x _im I=1, 2, …, n, sample object parameterization is achieved by constructing the argument U and the data matrix X:

U＝{x ₁ ,x ₂ ,…,x _n }，

wherein x is _im M kinds of data representing the i-th sample object;

step 1.2: standard translation and extreme degradation processing are carried out on the parameterized sample object:

in the method, in the process of the invention,

mean value of k-th data in n sample objects, s _k Representing the mean square error, x 'of the kth data in n sample objects' _ik A dimensionless value representing the kth data in the ith sample object,x″ _ik a calculated value representing the kth data in the ith sample object;

step 1.3: calculating the similarity degree between sample objects, and calculating the similarity degree r of the ith sample object and the jth sample object _ij ：

Sequentially calculating the similarity degree among all sample objects to form a similarity matrix R, and simplifying the similarity matrix R into a triangular matrix R ^* ：

Step 1.4: according to a triangular matrix R ^* Adopting a direct clustering method to obtain a clustering pedigree diagram;

step 1.5: presetting an initial threshold lambda, finding lambda with the best energy-saving effect through experimental design, and determining a driving working condition classification mode with the best energy-saving effect of the drive-by-wire chassis system;

step 1.6: the collected data are added into the domain U for processing, so that the real-time classification of the working conditions of the driver and the vehicle is realized;

Step 1.7: for the test design in step 1.5, a plurality of different thresholds lambda are taken to represent the similarity of the same class, lambda epsilon [0,1], and the larger the lambda value is, the larger the similarity is represented:

lambda is taken out ₁ For each sample object x =1 _i By similarity class, i.e. satisfying r _ij X=1 _i And x _j Constitute the similarity class, at this time, merge r _ij Sample object of=1 is a class, resulting in λ ₁ Equivalent classification at level=1;

lambda is taken out ₂ For the next largest value, the similarity is taken directly from R to be greater than or equal to lambda ₂ Element pair (x) _i ,x _j ) Will correspond to lambda ₁ Equivalent classification of x=1 _i Class and x of the location _j Merging the classes, and merging all the classes to obtain the lambda-base ₂ Equivalent classifications of (2);

lambda is taken out ₃ For the next largest value, the similarity is taken directly from R as lambda ₃ Element pair (x) _i ,x _j ) Will correspond to lambda ₂ X in the equivalence class of (2) _i Class and x of the location _j Merging the classes, and merging all the classes to obtain the lambda-base ₃ Equivalent classifications of (2);

and so on up to lambda _n =0, where U merges into one class;

step 2: the sorting from big to small according to the cluster analysis result of the relevant parameters of the ice, snow and muddy road conditions comprises: the working conditions of the simple ice and snow muddy road surface are 0% -40%, 40% -85% and 85% -100% of the working conditions of the conventional ice and snow muddy road surface; setting environment wet coefficient omega for different ice, snow and muddy road conditions _wet ：

Step 3: according to the road condition monitor in the road condition state sensing unit, the front end acquisition signal core sensor is used for sensing the change condition of road humidity and road viscosity degree parameters in the environment, the host acquisition system is used for rapidly analyzing and processing the change condition, data are transmitted to the server through a wireless network, real-time data such as road viscosity, dry and wet conditions and the like, namely a road viscosity factor lambda and a road humidity coefficient mu are obtained, and the height of a vehicle body which needs to be reduced under different ice, snow and muddy working conditions of different vehicle types is determined according to the following formula:

/>

wherein L is _i The wheelbase of the i-type vehicle is represented, and v represents the longitudinal speed of the vehicle;

according to the vehicle body height reduction data under the working conditions of different vehicle types, different speeds and different ice and snow muddy roads, the opening and closing of the electromagnetic valve are adjusted through the active suspension control unit to realize the inflation and deflation of the air spring and the damping of the damping-controlled continuously-adjustable shock absorber, so that the vehicle body height is adjusted.

The road condition sensing unit judges that the running road condition of the vehicle is a ramp road surface, and the ramp road surface comprises an ascending road surface and a descending road surface;

when the working condition is an uphill road, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a vehicle body height sensor arranged at the front suspension of the vehicle measures the vehicle body height displacement H _uf The vehicle body height sensor arranged at the rear suspension of the automobile measures the vehicle body height displacement H _ur A vehicle body pitch angle sensor mounted at the center of mass of the vehicle body measures the actual pitch angle θ of the vehicle body _ua The theoretical pitch angle theta of the vehicle body can be calculated according to the following formula _ut ：

Wherein L is the distance between a vehicle body height sensor at the front suspension and a vehicle body height sensor at the rear suspension;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut I is less than 0.8 °, and θ _ua When the angle is larger than 3 DEG, the data theta is calculated _ua Transmitting to the electronic control unit, the active suspension control unit executes a high-gradient mode, increases the height of the rear side of the automobile chassis, reduces the height of the front side of the automobile chassis, and reaches the displacement difference delta H of the front and rear heights of the automobile body _u ＝|H _uf -H _ur The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut I is less than 0.8 °, and θ _a When the angle is smaller than 3 DEG, the data theta is calculated _ua Transmitting to the electronic control unit, the active suspension control unit executes a low-gradient mode, and only increases the height of the rear side of the chassis of the automobile until the front-rear height displacement difference delta H of the automobile body _u ＝|H _uf -H _ur The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the carPitch angle deviation delta theta _u ＝|θ _ua -θ _ut When the I is larger than or equal to 0.8 degrees, the electronic control unit judges that the pitch angle measurement deviation is larger, the front and rear vehicle body height sensor data are required to be collected again, and then vehicle body pitch angle deviation comparison is carried out;

When the working condition is a downhill road, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a vehicle height sensor arranged at the front suspension of the vehicle measures the vehicle height displacement H _df The vehicle body height sensor arranged at the rear suspension of the automobile measures the vehicle body height displacement H _dr A vehicle body pitch angle sensor mounted at the center of mass of the vehicle body measures the actual pitch angle θ of the vehicle body _da The theoretical pitch angle theta of the vehicle body can be calculated according to the following formula _dt ：

Wherein L is the distance between a vehicle body height sensor at the front suspension and a vehicle body height sensor at the rear suspension;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt I is less than 0.8 °, and θ _da When the angle is larger than 3 DEG, the data theta is calculated _da Transmitting to the electronic control unit, the active suspension control unit executes a high-gradient mode, increases the height of the front side of the automobile chassis, reduces the height of the rear side of the automobile chassis, and reaches the displacement difference delta H of the front and rear heights of the automobile body _d ＝|H _df -H _dr The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt I is less than 0.8 °, and θ _da When the angle is smaller than 3 DEG, the data theta is calculated _da Transmitting to the electronic control unit, the active suspension control unit executes a low-gradient mode to only raise the height of the front side of the chassis of the automobile until the front-rear height displacement difference delta H of the automobile body _d ＝|H _df -H _dr The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the car body is pitchingAngular deviation delta theta _d ＝|θ _da -θ _dt When the I is larger than or equal to 0.8 degrees, the electronic control unit judges that the pitch angle measurement deviation is large, front and rear vehicle body height sensor data are required to be collected again, and then vehicle body pitch angle deviation comparison is carried out.

The road condition state sensing unit judges that the running road condition of the vehicle is a turning road surface;

the turning pavement comprises the following steps:

step 1: when the working condition is a turning road surface, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a front wheel steering angle measurement system acquires the front wheel steering angle delta of the vehicle _r The vehicle speed sensor acquires the vehicle turning speed v _r When the automobile runs normally, and the lateral acceleration is not more than 0.4g and the lateral deflection angle is not more than 5 degrees, the wheel lateral deflection force can be determined according to the following formula:

wherein F is _C1 ,F _C2 ,F _C3 ,F _C4 Indicating the sideways force of each wheel on the ground when turning; k (k) _f ,k _r Representing cornering stiffness of the front axle tire and the rear axle tire; beta represents the centroid slip angle; l (L) _f ,L _r Representing the distance of the centroid to the anterior and posterior axes; omega _z Indicating the angular velocity of the automobile when the automobile rotates around the Z axis;

considering the dynamics of the Z direction and the Y direction when the automobile turns, there are:

I _z

＝L _f (F _C1 +F _C2 )cosδ _r -L _r (F _C3 +F _C4 )，

mv _r (

+ω _z )＝(F _C1 +F _C2 )cosδ _r +(F _C3 +F _C4 )，

Wherein m represents the mass of the whole vehicle; i _z Indicating the angular velocity of the automobile when the automobile rotates around the Z axis; beta represents the centroid slip angle when the automobile rotates;

when the automobile turns, the load of the inner tyre is transferred to the outer wheel, and the transverse load transfer rate can be calculated according to the following formula:

wherein F is _zl ,F _zr Representing the vertical load of the left and right wheels, the sprung mass of the vehicle is not laterally displaced when ltr=0, and one wheel of the vehicle has been lifted off the ground when ltr= ±1;

step 2: in order to evaluate the rollover risk and rollover degree of an automobile during turning, a turning factor zeta is introduced, and the expression is as follows:

wherein Q is _a ,Q _b ,Q _c ,P _a ,P _b For the weighting coefficient, 0 < P _a ,P _b < 1, and P _a +P _b ＝1，0＜Q _a ,Q _b ,Q _c < 1; θ is the roll angle of the vehicle body,

is the roll angle speed of the vehicle body; a, a _y For lateral acceleration, a _yl Is critical lateral acceleration; LTR is the lateral load transfer rate, LTR _l Is critical lateral load transfer rate;

step 3: for i-typePreset turning factor zeta of vehicle _i The active suspension control unit executes the following strategy:

when the vehicle turns right, i.e. delta _r If the turning factor zeta is greater than the preset turning factor zeta of the i-type vehicle and is more than 0 _i When the vehicle is in a state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do stretching motion, the right front and right rear damping continuously adjustable shock absorber to do compression motion, the left front and left rear air springs are inflated, and the right front and right rear air springs are deflated until the vehicle body is horizontal; if the turning factor zeta is smaller than or equal to the preset turning factor zeta of the i-type vehicle _i When the vehicle is in a horizontal state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do stretching motion, and the left front and left rear air springs are inflated until the vehicle body is horizontal;

when the vehicle turns left, i.e. delta _r If the turning factor zeta is less than 0 and is greater than the preset turning factor zeta of the i-type vehicle _i When the vehicle is in a state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do compression motion, the right front and right rear damping continuously adjustable shock absorber to do stretching motion, the left front and left rear air springs are deflated, and the right front and right rear air springs are inflated until the vehicle body is horizontal; if the turning factor zeta is smaller than or equal to the preset turning factor zeta of the i-type vehicle _i And when the vehicle body is in a horizontal state, the active suspension control unit controls the i-type vehicle right front and right rear damping continuously adjustable shock absorber to do stretching motion, and the right front and right rear air springs are inflated.

The road condition state sensing unit judges that the running road condition of the vehicle is a level good road surface;

when the working condition is a level good road surface, the mode switching control unit adopts a weak perception mode, the longitudinal speed of the vehicle is obtained through a vehicle speed sensor in the sensing data acquisition unit, and the height of the vehicle body is adjusted through the active suspension control unit aiming at different vehicle types, and the method comprises the following steps:

Step 1: determining the height of the vehicle body to be reduced under different vehicle speeds of different vehicle types according to the following formula:

wherein H is _i Vehicle body lowering height representing i type, L _i Representing the wheelbase of an i-type vehicle, v _i Represents the longitudinal speed eta of the i-type vehicle _i Represents the chassis protection coefficient of the i model, wherein eta is more than or equal to 0.2 _i ≤0.3；

Step 2: according to the vehicle body height reduction data under different vehicle types and different speeds, the active suspension control unit adjusts the opening and closing of the electromagnetic valve to realize the inflation and deflation of the air spring and control the damping of the damping continuously adjustable shock absorber, so that the vehicle body height is adjusted.

Compared with the prior art, the invention has the beneficial effects that:

1. the control method of the active suspension of the automobile can perform execution control of the active suspension by actively collecting data and actively identifying road conditions, so that the level of a chassis is ensured, and the smoothness and the comfort of the automobile during running are improved.

2. The invention actively recognizes five road conditions, namely a bumpy road surface, an ice and snow muddy road surface, a ramp road surface, a turning road surface and a level good road surface, and carries out self-defined classification on vehicles, and different control methods are adopted by the active suspension aiming at different road conditions and different vehicle types, so that the uniqueness of the control methods under different conditions is ensured.

3. Aiming at different road working conditions, the sensing mode switching unit is divided into a strong sensing mode, a medium sensing mode and a weak sensing mode, so that the quantity and the types of the vehicle state parameters acquired by different sensing modes are different, and the vehicle can run smoothly, stably and safely.

Drawings

The invention is further described below with reference to the accompanying drawings:

FIG. 1 is a control framework diagram of an active suspension control method for an automobile according to the present invention;

FIG. 2 is a flow chart of operation when the vehicle is traveling on a bumpy road;

FIG. 3 is a flow chart of operation when the vehicle is traveling on a road with ice and snow and mud;

FIG. 4 is a flow chart of operation when the vehicle is traveling on a road condition that is a hill road surface;

FIG. 5 is a flowchart of operation when the vehicle is traveling on a road condition that is a cornering surface;

fig. 6 is a flowchart of the operation when the vehicle running road condition is a level good road surface.

Detailed Description

The invention will be described in further detail below with reference to the drawings and the specific examples.

As shown in FIG. 1, the invention relates to an active suspension control method of an automobile, which comprises a sensing data acquisition unit, a road condition state sensing unit, a mode switching control unit, an expert data calibration unit, a closed-loop control force correction unit and an active suspension control unit.

The sensing data acquisition unit comprises a centroid side deflection angle sensor, a vehicle body side inclination angle sensor, a vehicle body vertical acceleration sensor, a vehicle body pitch angle sensor, a cab camera, a vehicle speed sensor, a vehicle body height sensor and a front wheel steering angle measuring system; the method is used for respectively obtaining a centroid side deflection angle, a vehicle body side inclination angle, a vehicle body vertical acceleration, a vehicle body pitch angle, a driver peripheral swing distance, a vehicle longitudinal speed, a suspension height change and a front wheel corner; according to the collected data, a bumping factor is designed for evaluating the comprehensive performance of the bumping degree of the bumpy road surface; introducing a turning factor for evaluating the rollover risk and the rollover degree of the automobile during turning;

the road condition sensing unit comprises a map, a navigation, a camera, a road condition database and a road condition monitor; the navigation and map is used for acquiring the current vehicle position; the camera is used for acquiring barriers, road gradient and ground concave-convex degree of the front side, the rear side and the lateral side of the vehicle; the road working condition database judges the road working conditions according to the current vehicle position, the obstacle, the road gradient, the ground concave-convex degree and the off-line road database, including but not limited to bumpy road surfaces, ice and snow muddy road surfaces, ramp road surfaces, turning road surfaces and horizontal good road surfaces; the road surface condition monitor comprises a front end acquisition signal core sensor, a host acquisition system, a wireless network and a server, and is used for monitoring the changes of real-time data such as road surface ponding, snow thickness, rain and snow quantity, dry and wet conditions and the like and obtaining road viscosity factors and road humidity coefficients; analyzing different ice, snow and muddy road conditions by a cluster analysis method, and setting an environment wet coefficient;

The mode switching control unit comprises a strong sensing mode, a medium sensing mode and a weak sensing mode, different sensing modes are adopted according to the conditions of different identified roads, and the quantity and the types of vehicle state parameters acquired by the different sensing modes are different;

the expert data calibration unit comprises the steps of selecting 100 different bumpy road conditions for a plurality of custom types of vehicles to simulate, calibrate and empirically analyze, so as to form active suspension control force output of the vehicles of different types under different speeds and different road conditions, and integrating an expert database;

the closed-loop control force correction unit comprises a closed-loop correction function constructed by a centroid side deflection angle, a vehicle body side inclination angle, a vehicle body vertical acceleration and a vehicle body pitch angle which are acquired by the sensing data acquisition unit, so as to obtain correction forces of different self-defined vehicle types and further correct the active suspension control force;

the active suspension control unit comprises a pressure sensor, a height sensor, an air spring, a damping continuously adjustable shock absorber, an electromagnetic valve, an air pump, an air storage tank and an electronic control unit.

As shown in fig. 2, the road condition sensing unit determines that the running road condition of the vehicle is a bumpy road surface;

when the working condition is bumpy road surface, the mode switching control unit adopts a strong sensing mode, and a centroid slip angle sensor in the sensing data acquisition unit acquires a centroid slip angle beta and a weight coefficient

The value range is 0 to 1,/for>

A smaller value means that the smaller the degree of cornering of the vehicle during movement, the better the steering stability, and +.>

When the centroid side deflection angle is 0 degrees; />

The larger means that the greater the degree of cornering of the vehicle during movement, the poorer the steering stability, and +.>

When the centroid side deflection angle is 90 degrees;

calculating a root mean square value of the centroid slip angle according to the following formula:

wherein: beta _t The centroid side deflection angle acquired at the moment t;

N ₁ the number of sampling the centroid slip angle is N ₁ ＝T/ns ₁ ；

T is a time period;

ns ₁ the signal acquisition period is the centroid side deflection angle signal;

the body roll angle sensor in the sensing data acquisition unit acquires the body roll angle

Weight coefficient

The value range is 0 to 1,/for>

Smaller means that the vehicle is less tilted during movement, the lower the probability of rollover of the vehicle,

when the roll angle of the vehicle body is 0 degree; />

A larger value indicates a larger degree of roll of the vehicle during movement, and a higher probability of rollover of the vehicle is +.>

When the roll angle of the vehicle body is 90 degrees;

the root mean square value of the roll angle of the vehicle body is calculated according to the following formula:

wherein:

the roll angle of the vehicle body is acquired at the moment t;

N ₂ the number of the sampled roll angles of the vehicle body is N ₂ ＝T/ns ₂ ；

T is a time period;

ns ₂ the method comprises the steps of acquiring a vehicle body roll angle signal;

The vehicle body vertical acceleration sensor in the sensing data acquisition unit acquires vehicle body vertical acceleration a _z Weight coefficient

The value range is 0 to 1,/for>

The smaller the vertical vibration of the vehicle in the moving process is, the lower the probability that the wheels are separated from the ground is, the better the riding comfort is, and the more>

When the vehicle does not vibrate vertically; />

The larger the vertical vibration of the vehicle in the moving process is, the higher the probability that the wheels are separated from the ground is, the worse the riding comfort is, and the more the vehicle is>

Indicating that the wheel is separated from the ground;

the root mean square value of the vertical acceleration of the vehicle body is calculated according to the following formula:

wherein: a, a _zt The vertical acceleration of the vehicle body is acquired at the moment t;

N ₃ the number of samples of the vertical acceleration of the vehicle body is N ₃ ＝T/ns ₃ ；

T is a time period;

ns ₃ the method is characterized in that the method is a vehicle body vertical acceleration signal acquisition period;

the vehicle body pitch angle sensor in the sensing data acquisition unit acquires a vehicle body pitch angle theta and a weight coefficient

The value range is 0 to 1,/for>

Smaller means that the pitch degree of the vehicle is smaller during the movement, the difference in height between the front and rear suspensions of the vehicle is smaller,/>

The time indicates that the vehicle runs smoothly; />

The larger the pitch degree of the vehicle in the moving process, the larger the height difference between front and rear suspensions of the vehicle, and the greater the +.>

The time indicates that the vehicle turns upward or turns downward;

Calculating the root mean square value of the pitch angle of the vehicle body according to the following formula:

wherein: θ _t The pitch angle of the vehicle body is acquired at the moment t;

N ₄ the pitch angle of the vehicle body is sampled by the number N ₄ ＝T/ns ₄ ；

T is a time period;

ns ₄ the pitch angle signal acquisition period of the vehicle body;

the cab camera in the sensing data acquisition unit acquires a driver pendulum distance s and a pendulum weight coefficient

The value range is 0 to 1, when a driver drives on a bumpy road, the driver can shake in the front, back, left and right directions due to the bumpy road, and the smaller the shaking amplitude is, the smaller the circumferential distance is, and the smaller the influence of the bumpy road on the driver is; the larger the swing amplitude is, the larger the swing distance is, and the larger the influence of road jolting on a driver is;

the root mean square value of the driver's turn distance is calculated according to the following formula:

wherein: s is(s) _t The driver circle swing distance acquired at the time t;

N ₅ sampling the number of the driver circle swing distances, N ₅ ＝T/ns ₅ ；

T is a time period;

ns ₅ the method comprises the steps of (1) setting a distance signal acquisition period for a driver;

designing a comprehensive performance index function for evaluating the bumping degree of a bumpy road surface:

the conversion into matrix form is as follows:

wherein ρ is a jolt factor, Q _e Correcting the matrix for the parameter weight, wherein

Is 1 x 1 gaussian white noise.

Because the performance requirements on different vehicle types are different under the same road surface, the vehicle types are customized to be divided into A-type vehicles, B-type vehicles and C-type vehicles according to the different vehicle types, wherein the A-type vehicles are small vehicles with the wheelbase of less than 2700mm, the B-type vehicles are medium-sized vehicles with the wheelbase of between 2700 and 2850mm, and the C-type vehicles are large vehicles with the wheelbase of more than 2850 mm; hereinafter, i-type vehicle, wherein i takes a value of A, B, C;

for type A vehicles, the preset pitch factor range is [ ρ ] _Amin ,ρ _Amax ]When ρ < ρ _Amin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Amin ≤ρ≤ρ _Amax When the vehicle speed is lower than 65km/h, the vehicle is judged to be in a bumpy low risk zone, when the vehicle speed is higher than 65km/h and lower than 70km/h, the vehicle is judged to be in a bumpy medium risk zone, and when the vehicle speed is higher than 70km/h, the vehicle is judged to be in a bumpy high risk zone; when ρ > ρ _Amax When the vehicle is judged to be in a bumpy high risk interval;

for type B vehicles, the preset pitch factor range is [ ρ ] _Bmin ,ρ _Bmax ]When ρ < ρ _Bmin When the vehicle is judged to be atIn a bump low risk zone; when ρ is _Bmin ≤ρ≤ρ _Bmax When the vehicle speed is lower than 55km/h, the vehicle is judged to be in a bumpy low risk interval, when the vehicle speed is higher than 55km/h and lower than 60km/h, the vehicle is judged to be in a bumpy medium risk interval, and when the vehicle speed is higher than 60km/h, the vehicle is judged to be in a bumpy high risk interval; when ρ > ρ _Bmax When the vehicle is judged to be in a bumpy high risk interval;

for a C-type vehicle, the preset bump factor range is [ ρ ] _Cmin ,ρ _Cmax ]When ρ < ρ _Cmin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Cmin ≤ρ≤ρ _Cmax When the vehicle speed is lower than 45km/h, the vehicle is judged to be in a bumpy low risk zone, when the vehicle speed is higher than 45km/h and lower than 50km/h, the vehicle is judged to be in a bumpy medium risk zone, and when the vehicle speed is higher than 50km/h, the vehicle is judged to be in a bumpy high risk zone; when ρ > ρ _Cmax When the vehicle is judged to be in the bump high risk section.

The expert data calibration unit comprises the following steps:

step 1: selecting 100 different bumpy road conditions for different types of vehicles, performing simulation, real vehicle calibration and experience analysis to form an i-type vehicle active suspension control force output under different vehicle speeds and different road conditions, and forming an expert database;

step 2: according to the fact that the vehicles of different vehicle types are in different bumpy risk intervals and different vehicle speeds, the expert database can be compared to obtain that the active suspension control force required by the four wheels on the left side and the right side of the i-type vehicle is [ F ] _iFL F _iFR F _iRL F _iRR ]；

Wherein F is _iFL Active suspension control force for left front wheel of i-type vehicle, F _iFR Active suspension control force for right front wheel of i-type vehicle, F _iRL Active suspension control force for left rear wheel of i-type vehicle, F _iRR The control force is actively controlled by the suspension of the right rear wheel of the i-type vehicle.

The closed-loop control force correction unit is used for correcting the four wheel active suspension control forces in the scheme; for the roll angle beta and the roll angle of the vehicle body according to the mass center

Vertical acceleration a of vehicle body _z Constructing an i-type vehicle closed loop correction function by using a vehicle body pitch angle theta>

Calculating the i-type vehicle closed loop correction force F _ib ＝k _i f _i Wherein k is _i The closed loop correction function coefficient of the i-type vehicle is restricted to 0 < k _i Is less than or equal to 1; optimal active suspension control force output of i-type vehicle: />

Wherein F is _iZFL Outputting control force for optimal active suspension of left front wheel of i-type vehicle, F _iZFR Outputting control force for optimal active suspension of right front wheel of i-type vehicle, F _iZRL Outputting control force for the optimal active suspension of the left rear wheel of the i-type vehicle, F _iZRR Outputting control force for the optimal active suspension of the right rear wheel of the i-type vehicle;

the electronic control unit in the active suspension control unit receives the optimal active suspension output control force of four wheels, realizes the adjustment of the vehicle body posture by adjusting the opening and closing of electromagnetic valves to realize the inflation and deflation of the air spring and the damping of the damping continuously adjustable shock absorber, and adjusts the rigidity of the air spring of the active suspension and the damping of the damping continuously adjustable shock absorber by utilizing proportional-integral-differential closed loop feedback control.

As shown in fig. 3, the road condition sensing unit determines that the running road condition of the vehicle is ice, snow and muddy road;

the ice and snow muddy road surface comprises the following steps:

step 1: when the working condition is ice and snow muddy road, the mode switching control unit adopts a strong sensing mode to perform clustering analysis on relevant parameters of the ice and snow muddy road working condition, and the specific steps are as follows:

step 1.1: setting n sample objects, using x ₁ ,x ₂ ,…,x _n A representation; multiple time period data acquisition during vehicle driving, each sample object packageContaining m data indices x _i1 ,x _i2 ,…,x _im I=1, 2, …, n, sample object parameterization is achieved by constructing the argument U and the data matrix X:

U＝{x ₁ ,x ₂ ,…,x _n }，

wherein x is _im M kinds of data representing the i-th sample object;

step 1.2: standard translation and extreme degradation processing are carried out on the parameterized sample object:

in the method, in the process of the invention,

mean value of k-th data in n sample objects, s _k Represents the kth in n sample objects

The mean square error of the data is calculated,

dimensionless values representing kth data in the ith sample object, +.>

A calculated value representing the kth data in the ith sample object;

step 1.3: calculation ofDegree of similarity between sample objects, i-th and j-th sample objects, degree of similarity r _ij ：

Sequentially calculating the similarity degree among all sample objects to form a similarity matrix R, and simplifying the similarity matrix R into a triangular matrix R ^* ：

Step 1.4: according to a triangular matrix R ^* Adopting a direct clustering method to obtain a clustering pedigree diagram;

step 1.5: presetting an initial threshold lambda, finding lambda with the best energy-saving effect through experimental design, and determining a driving working condition classification mode with the best energy-saving effect of the drive-by-wire chassis system;

step 1.6: the collected data are added into the domain U for processing, so that the real-time classification of the working conditions of the driver and the vehicle is realized;

step 1.7: for the test design in step 1.5, a plurality of different thresholds lambda are taken to represent the similarity of the same class, lambda epsilon [0,1], and the larger the lambda value is, the larger the similarity is represented:

lambda is taken out ₁ For each sample object x =1 _i By similarity class, i.e. satisfying r _ij X=1 _i And x _j Constitute the similarity class, at this time, merge r _ij Sample object of=1 is a class, resulting in λ ₁ Equivalent classification at level=1;

lambda is taken out ₂ For the next largest value, the similarity is taken directly from R to be greater than or equal to lambda ₂ Element pair (x) _i ,x _j ) Will correspond to lambda ₁ Equivalent classification of x=1 _i Class and x of the location _j Merging the classes, and merging all the classes to obtain the lambda-base ₂ Equivalent classifications of (2);

Lambda is taken out ₃ For the next largest value, the similarity is taken directly from R as lambda ₃ Element pair (x) _i ,x _j ) Will correspond to lambda ₂ X in the equivalence class of (2) _i Class and x of the location _j Merging the classes, and merging all the classes to obtain the lambda-base ₃ Equivalent classifications of (2);

and so on up to lambda _n =0, where U merges into one class;

step 2: the sorting from big to small according to the cluster analysis result of the relevant parameters of the ice, snow and muddy road conditions comprises: the working conditions of the simple ice and snow muddy road surface are 0% -40%, 40% -85% and 85% -100% of the working conditions of the conventional ice and snow muddy road surface; setting environment wet coefficient omega for different ice, snow and muddy road conditions _wet ：

Step 3: according to the road condition monitor in the road condition state sensing unit, the front end acquisition signal core sensor is used for sensing the change condition of road humidity and road viscosity degree parameters in the environment, the host acquisition system is used for rapidly analyzing and processing the change condition, data are transmitted to the server through a wireless network, real-time data such as road viscosity, dry and wet conditions and the like, namely a road viscosity factor lambda and a road humidity coefficient mu are obtained, and the height of a vehicle body which needs to be reduced under different ice, snow and muddy working conditions of different vehicle types is determined according to the following formula:

Wherein L is _i The wheelbase of the i-type vehicle is represented, and v represents the longitudinal speed of the vehicle;

according to the vehicle body height reduction data under the working conditions of different vehicle types, different speeds and different ice and snow muddy roads, the opening and closing of the electromagnetic valve are adjusted through the active suspension control unit to realize the inflation and deflation of the air spring and the damping of the damping-controlled continuously-adjustable shock absorber, so that the vehicle body height is adjusted.

As shown in fig. 4, the road condition sensing unit determines that the running road condition of the vehicle is a ramp road surface, and the ramp road surface comprises an ascending road surface and a descending road surface;

when the working condition is an uphill road, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a vehicle body height sensor arranged at the front suspension of the vehicle measures the vehicle body height displacement H _uf The vehicle body height sensor arranged at the rear suspension of the automobile measures the vehicle body height displacement H _ur A vehicle body pitch angle sensor mounted at the center of mass of the vehicle body measures the actual pitch angle θ of the vehicle body _ua The theoretical pitch angle theta of the vehicle body can be calculated according to the following formula _ut ：

Wherein L is the distance between a vehicle body height sensor at the front suspension and a vehicle body height sensor at the rear suspension;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut I is less than 0.8 °, and θ _ua When the angle is larger than 3 DEG, the data theta is calculated _ua Transmitting to the electronic control unit, the active suspension control unit executes a high-gradient mode, increases the height of the rear side of the automobile chassis, reduces the height of the front side of the automobile chassis, and reaches the displacement difference delta H of the front and rear heights of the automobile body _u ＝|H _uf -H _ur The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut I is less than 0.8 °, and θ _a When the angle is smaller than 3 DEG, the data theta is calculated _ua Transmitting to the electronic control unit, the active suspension control unit executes a low-gradient mode, and only increases the height of the rear side of the chassis of the automobile until the front-rear height displacement difference delta H of the automobile body _u ＝|H _uf -H _ur The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut When the I is more than or equal to 0.8 degrees, electronic control is performedThe unit judges that the pitch angle measurement deviation is larger, the front and rear vehicle body height sensor data are required to be collected again, and then the vehicle body pitch angle deviation comparison is carried out;

when the working condition is a downhill road, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a vehicle height sensor arranged at the front suspension of the vehicle measures the vehicle height displacement H _df The vehicle body height sensor arranged at the rear suspension of the automobile measures the vehicle body height displacement H _dr A vehicle body pitch angle sensor mounted at the center of mass of the vehicle body measures the actual pitch angle θ of the vehicle body _da The theoretical pitch angle theta of the vehicle body can be calculated according to the following formula _dt ：

Wherein L is the distance between a vehicle body height sensor at the front suspension and a vehicle body height sensor at the rear suspension;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt I is less than 0.8 °, and θ _da When the angle is larger than 3 DEG, the data theta is calculated _da Transmitting to the electronic control unit, the active suspension control unit executes a high-gradient mode, increases the height of the front side of the automobile chassis, reduces the height of the rear side of the automobile chassis, and reaches the displacement difference delta H of the front and rear heights of the automobile body _d ＝|H _df -H _dr The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt I is less than 0.8 °, and θ _da When the angle is smaller than 3 DEG, the data theta is calculated _da Transmitting to the electronic control unit, the active suspension control unit executes a low-gradient mode to only raise the height of the front side of the chassis of the automobile until the front-rear height displacement difference delta H of the automobile body _d ＝|H _df -H _dr The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt When the I is more than or equal to 0.8 degrees, the electronic control unit judgesThe measurement deviation of the broken pitch angle is larger, front and rear vehicle body height sensor data are required to be acquired again, and then the vehicle body pitch angle deviation is compared.

As shown in fig. 5, the road condition sensing unit determines that the running road condition of the vehicle is a turning road surface;

the turning pavement comprises the following steps:

step 1: when the working condition is a turning road surface, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a front wheel steering angle measurement system acquires the front wheel steering angle delta of the vehicle _r The vehicle speed sensor acquires the vehicle turning speed v _r When the automobile runs normally, and the lateral acceleration is not more than 0.4g and the lateral deflection angle is not more than 5 degrees, the wheel lateral deflection force can be determined according to the following formula:

wherein F is _C1 ,F _C2 ,F _C3 ,F _C4 Indicating the sideways force of each wheel on the ground when turning; k (k) _f ,k _r Representing cornering stiffness of the front axle tire and the rear axle tire; beta represents the centroid slip angle; l (L) _f ,L _r Representing the distance of the centroid to the anterior and posterior axes; omega _z Indicating the angular velocity of the automobile when the automobile rotates around the Z axis;

considering the dynamics of the Z direction and the Y direction when the automobile turns, there are:

I _z

＝L _f (F _C1 +F _C2 )cosδ _r -L _r (F _C3 +F _C4 )，

mv _r (

+ω _z )＝(F _C1 +F _C2 )cosδ _r +(F _C3 +F _C4 )，

wherein m represents the mass of the whole vehicle; i _z Indicating the angular velocity of the automobile when the automobile rotates around the Z axis; beta represents the centroid slip angle when the automobile rotates;

when the automobile turns, the load of the inner tyre is transferred to the outer wheel, and the transverse load transfer rate can be calculated according to the following formula:

wherein F is _zl ,F _zr Representing the vertical load of the left and right wheels, the sprung mass of the vehicle is not laterally displaced when ltr=0, and one wheel of the vehicle has been lifted off the ground when ltr= ±1;

step 2: in order to evaluate the rollover risk and rollover degree of an automobile during turning, a turning factor zeta is introduced, and the expression is as follows:

wherein Q is _a ,Q _b ,Q _c ,P _a ,P _b For the weighting coefficient, 0 < P _a ,P _b < 1, and P _a +P _b ＝1，0＜Q _a ,Q _b ,Q _c ＜1；

The vehicle body side inclination angle is the vehicle body side inclination angle speed; a, a _y For lateral acceleration, a _yl Is critical lateral acceleration; LTR is the lateral load transfer rate, LTR _l Is critical lateral load transfer rate;

step 3: for the purpose ofPreset turning factor zeta of i-type vehicle _i The active suspension control unit executes the following strategy:

when the vehicle turns right, i.e. delta _r If the turning factor zeta is greater than the preset turning factor zeta of the i-type vehicle and is more than 0 _i When the vehicle is in a state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do stretching motion, the right front and right rear damping continuously adjustable shock absorber to do compression motion, the left front and left rear air springs are inflated, and the right front and right rear air springs are deflated until the vehicle body is horizontal; if the turning factor zeta is smaller than or equal to the preset turning factor zeta of the i-type vehicle _i When the vehicle is in a horizontal state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do stretching motion, and the left front and left rear air springs are inflated until the vehicle body is horizontal;

When the vehicle turns left, i.e. delta _r If the turning factor zeta is less than 0 and is greater than the preset turning factor zeta of the i-type vehicle _i When the vehicle is in a state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do compression motion, the right front and right rear damping continuously adjustable shock absorber to do stretching motion, the left front and left rear air springs are deflated, and the right front and right rear air springs are inflated until the vehicle body is horizontal; if the turning factor zeta is smaller than or equal to the preset turning factor zeta of the i-type vehicle _i And when the vehicle body is in a horizontal state, the active suspension control unit controls the i-type vehicle right front and right rear damping continuously adjustable shock absorber to do stretching motion, and the right front and right rear air springs are inflated.

As shown in fig. 6, the road condition sensing unit determines that the running road condition of the vehicle is a level good road surface;

when the working condition is a level good road surface, the mode switching control unit adopts a weak perception mode, the longitudinal speed of the vehicle is obtained through a vehicle speed sensor in the sensing data acquisition unit, and the height of the vehicle body is adjusted through the active suspension control unit aiming at different vehicle types, and the method comprises the following steps:

step 1: determining the height of the vehicle body to be reduced under different vehicle speeds of different vehicle types according to the following formula:

Wherein H is _i Vehicle body lowering height representing i type, L _i Representing the wheelbase of an i-type vehicle, v _i Represents the longitudinal speed eta of the i-type vehicle _i Represents the chassis protection coefficient of the i model, wherein eta is more than or equal to 0.2 _i ≤0.3；

Step 2: according to the vehicle body height reduction data under different vehicle types and different speeds, the active suspension control unit adjusts the opening and closing of the electromagnetic valve to realize the inflation and deflation of the air spring and control the damping of the damping continuously adjustable shock absorber, so that the vehicle body height is adjusted.

Claims (9)

1. An active suspension control method for an automobile is characterized by comprising the following steps: the system comprises a sensing data acquisition unit, a road condition sensing unit, a mode switching control unit, an expert data calibration unit, a closed-loop control force correction unit and an active suspension control unit;

the sensing data acquisition unit comprises a centroid side deflection angle sensor, a vehicle body side inclination angle sensor, a vehicle body vertical acceleration sensor, a vehicle body pitch angle sensor, a cab camera, a vehicle speed sensor, a vehicle body height sensor and a front wheel steering angle measuring system; the method is used for respectively obtaining a centroid side deflection angle, a vehicle body side inclination angle, a vehicle body vertical acceleration, a vehicle body pitch angle, a driver peripheral swing distance, a vehicle longitudinal speed, a suspension height change and a front wheel corner; according to the collected data, a bumping factor is designed for evaluating the comprehensive performance of the bumping degree of the bumpy road surface; introducing a turning factor for evaluating the rollover risk and the rollover degree of the automobile during turning;

The road condition sensing unit comprises a map, a navigation, a camera, a road condition database and a road condition monitor; the navigation and map is used for acquiring the current vehicle position; the camera is used for acquiring barriers, road gradient and ground concave-convex degree of the front side, the rear side and the lateral side of the vehicle; the road working condition database judges the road working conditions according to the current vehicle position, the obstacle, the road gradient, the ground concave-convex degree and the off-line road database, including but not limited to bumpy road surfaces, ice and snow muddy road surfaces, ramp road surfaces, turning road surfaces and horizontal good road surfaces; the road surface condition monitor comprises a front end acquisition signal core sensor, a host acquisition system, a wireless network and a server, and is used for monitoring the changes of real-time data such as road surface ponding, snow thickness, rain and snow quantity, dry and wet conditions and the like and obtaining road viscosity factors and road humidity coefficients; analyzing different ice, snow and muddy road conditions by a cluster analysis method, and setting an environment wet coefficient;

the mode switching control unit comprises a strong sensing mode, a medium sensing mode and a weak sensing mode, different sensing modes are adopted according to the conditions of different identified roads, and the quantity and the types of vehicle state parameters acquired by the different sensing modes are different;

The expert data calibration unit comprises the steps of selecting 100 different bumpy road conditions for a plurality of custom types of vehicles to simulate, calibrate and empirically analyze, so as to form active suspension control force output of the vehicles under different speeds and different road conditions, and integrating an expert database;

the closed-loop control force correction unit comprises a closed-loop correction function constructed by a centroid side deflection angle, a vehicle body side inclination angle, a vehicle body vertical acceleration and a vehicle body pitch angle which are acquired by the sensing data acquisition unit, so as to obtain correction forces of different self-defined vehicle types and further correct the active suspension control force;

the active suspension control unit comprises a pressure sensor, a height sensor, an air spring, a damping continuously adjustable shock absorber, an electromagnetic valve, an air pump, an air storage tank and an electronic control unit.

2. The method for controlling an active suspension of an automobile according to claim 1, wherein the road condition sensing unit determines that the running road condition of the automobile is a bumpy road;

when the working condition is bumpy road surface, the mode switching control unit adopts a strong sensing mode, and a centroid slip angle sensor in the sensing data acquisition unit acquires a centroid slip angle beta and a weight coefficient

The value range is 0 to 1,/for >

A smaller value means that the smaller the degree of cornering of the vehicle during movement, the better the steering stability, and +.>

When the centroid side deflection angle is 0 degrees; />

The larger means that the greater the degree of cornering of the vehicle during movement, the poorer the steering stability, and +.>

When the centroid side deflection angle is 90 degrees;

calculating a root mean square value of the centroid slip angle according to the following formula:

wherein: beta _t The centroid side deflection angle acquired at the moment t;

N ₁ the number of sampling the centroid slip angle is N ₁ ＝T/ns ₁ ；

T is a time period;

ns ₁ the signal acquisition period is the centroid side deflection angle signal;

the body roll angle sensor in the sensing data acquisition unit acquires the body roll angle

Weight coefficient->

The value range is 0 to 1,/for>

Smaller means that the vehicle is tilted to a lesser extent during movement, the probability of rollover of the vehicle is lower, +.>

When the roll angle of the vehicle body is 0 degree; />

A larger value indicates a greater degree of roll of the vehicle during movement, a higher probability of rollover of the vehicle,

when the roll angle of the vehicle body is 90 degrees;

the root mean square value of the roll angle of the vehicle body is calculated according to the following formula:

wherein:

the roll angle of the vehicle body is acquired at the moment t;

N ₂ the number of the sampled roll angles of the vehicle body is N ₂ ＝T/ns ₂ ；

T is a time period;

ns ₂ the method comprises the steps of acquiring a vehicle body roll angle signal;

the vehicle body vertical acceleration sensor in the sensing data acquisition unit acquires vehicle body vertical acceleration a _z Weight coefficient

The value range is 0 to 1,/for>

The smaller the vertical vibration of the vehicle in the moving process is, the lower the probability that the wheels are separated from the ground is, the better the riding comfort is, and the more>

When the vehicle does not vibrate vertically; />

The larger the vertical vibration of the vehicle in the moving process is, the higher the probability that the wheels are separated from the ground is, the worse the riding comfort is, and the more the vehicle is>

Indicating that the wheel is separated from the ground;

the root mean square value of the vertical acceleration of the vehicle body is calculated according to the following formula:

wherein: a, a _zt The vertical acceleration of the vehicle body is acquired at the moment t;

N ₃ the number of samples of the vertical acceleration of the vehicle body is N ₃ ＝T/ns ₃ ；

T is a time period;

ns ₃ the method is characterized in that the method is a vehicle body vertical acceleration signal acquisition period;

the vehicle body pitch angle sensor in the sensing data acquisition unit acquires a vehicle body pitch angle theta and a weight coefficient

The value range is 0 to 1,/for>

Smaller means that the pitch degree of the vehicle is smaller during the movement, the difference in height between the front and rear suspensions of the vehicle is smaller,/>

The time indicates that the vehicle runs smoothly; />

The larger the pitch degree of the vehicle in the moving process, the larger the height difference between front and rear suspensions of the vehicle, and the greater the +.>

The time indicates that the vehicle turns upward or turns downward;

calculating the root mean square value of the pitch angle of the vehicle body according to the following formula:

wherein: θ _t The pitch angle of the vehicle body is acquired at the moment t;

N ₄ The pitch angle of the vehicle body is sampled by the number N ₄ ＝T/ns ₄ ；

T is a time period;

ns ₄ the pitch angle signal acquisition period of the vehicle body;

the cab camera in the sensing data acquisition unit acquires a driver pendulum distance s and a pendulum weight coefficient

The value range is 0 to 1, when a driver drives on a bumpy road, the driver can shake in the front, back, left and right directions due to the bumpy road, and the smaller the shaking amplitude is, the smaller the circumferential distance is, and the smaller the influence of the bumpy road on the driver is; the larger the swing amplitude is, the larger the swing distance is, and the larger the influence of road jolting on a driver is;

the root mean square value of the driver's turn distance is calculated according to the following formula:

wherein: s is(s) _t The driver circle swing distance acquired at the time t;

N ₅ sampling the number of the driver circle swing distances, N ₅ ＝T/ns ₅ ；

T is a time period;

ns ₅ the method comprises the steps of (1) setting a distance signal acquisition period for a driver;

designing a comprehensive performance index function for evaluating the bumping degree of a bumpy road surface:

the conversion into matrix form is as follows:

wherein ρ is a jolt factor, Q _e Correcting moments for parameter weightsAn array in which

Is 1 x 1 gaussian white noise.

3. The method for controlling the active suspension of the automobile according to claim 2, wherein the performance requirements of different automobile types are different under the same road surface, the automobile types are divided into an A-type automobile, a B-type automobile and a C-type automobile according to the different automobile types, wherein the A-type automobile is a small-sized automobile with a wheelbase of less than 2700mm, the B-type automobile is a medium-sized automobile with a wheelbase of between 2700 and 2850mm, and the C-type automobile is a large-sized automobile with a wheelbase of more than 2850 mm; hereinafter, i-type vehicle, wherein i takes a value of A, B, C;

For type A vehicles, the preset pitch factor range is [ ρ ] _Amin ,ρ _Amax ]When ρ < ρ _Amin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Amin ≤ρ≤ρ _Amax When the vehicle speed is lower than 65km/h, the vehicle is judged to be in a bumpy low risk zone, when the vehicle speed is higher than 65km/h and lower than 70km/h, the vehicle is judged to be in a bumpy medium risk zone, and when the vehicle speed is higher than 70km/h, the vehicle is judged to be in a bumpy high risk zone; when ρ > ρ _Amax When the vehicle is judged to be in a bumpy high risk interval;

for type B vehicles, the preset pitch factor range is [ ρ ] _Bmin ,ρ _Bmax ]When ρ < ρ _Bmin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Bmin ≤ρ≤ρ _Bmax When the vehicle speed is lower than 55km/h, the vehicle is judged to be in a bumpy low risk interval, when the vehicle speed is higher than 55km/h and lower than 60km/h, the vehicle is judged to be in a bumpy medium risk interval, and when the vehicle speed is higher than 60km/h, the vehicle is judged to be in a bumpy high risk interval; when ρ > ρ _Bmax When the vehicle is judged to be in a bumpy high risk interval;

for a C-type vehicle, the preset bump factor range is [ ρ ] _Cmin ,ρ _Cmax ]When ρ < ρ _Cmin When the vehicle is judged to be in a bumpy low risk zone; when ρ is _Cmin ≤ρ≤ρ _Cmax When the vehicle speed is lower than 45km/h, the vehicle is judged to be in a bumpy low risk zone, when the vehicle speed is higher than 45km/h and lower than 50km/h, the vehicle is judged to be in a bumpy medium risk zone, and when the vehicle speed is higher than 50km/h, the vehicle is judged to be in a bumpy high risk zone; when ρ > ρ _Cmax When the vehicle is judged to be in the bump high risk section.

4. The method of claim 1, wherein the expert data calibration unit comprises the steps of:

step 1: selecting 100 different bumpy road conditions for different types of vehicles, performing simulation, real vehicle calibration and experience analysis to form an i-type vehicle active suspension control force output under different vehicle speeds and different road conditions, and forming an expert database;

step 2: according to the method, according to claim 3, the vehicle of different types is in different bumpy risk intervals and different vehicle speeds, and the active suspension control force required by four wheels on the left and right sides of the i-type vehicle can be obtained by comparing the expert database to be [ F _iFL F _iFR F _iRL F _iRR ]；

Wherein F is _iFL Active suspension control force for left front wheel of i-type vehicle, F _iFR Active suspension control force for right front wheel of i-type vehicle, F _iRL Active suspension control force for left rear wheel of i-type vehicle, F _iRR The control force is actively controlled by the suspension of the right rear wheel of the i-type vehicle.

5. The method according to claim 1, wherein the closed-loop control force correction unit is configured to correct four wheel active suspension control forces in claim 4; for the roll angle beta and the roll angle of the vehicle body according to the mass center

Vertical acceleration a of vehicle body _z Construction of i-type vehicle closure by vehicle body pitch angle thetaRing correction function

Calculating the i-type vehicle closed loop correction force F _ib ＝k _i f _i Wherein k is _i The closed loop correction function coefficient of the i-type vehicle is restricted to 0 < k _i Is less than or equal to 1; optimal active suspension control force output of i-type vehicle: />

Wherein F is _iZFL Outputting control force for optimal active suspension of left front wheel of i-type vehicle, F _iZFR Outputting control force for optimal active suspension of right front wheel of i-type vehicle, F _iZRL Outputting control force for the optimal active suspension of the left rear wheel of the i-type vehicle, F _iZRR Outputting control force for the optimal active suspension of the right rear wheel of the i-type vehicle;

the electronic control unit in the active suspension control unit receives the optimal active suspension output control force of four wheels, realizes the adjustment of the vehicle body posture by adjusting the opening and closing of electromagnetic valves to realize the inflation and deflation of the air spring and the damping of the damping continuously adjustable shock absorber, and adjusts the rigidity of the air spring of the active suspension and the damping of the damping continuously adjustable shock absorber by utilizing proportional-integral-differential closed loop feedback control.

6. The method for controlling an active suspension of an automobile according to claim 1, wherein the road condition sensing unit determines that the running road condition of the automobile is ice, snow and mud;

the ice and snow muddy road surface comprises the following steps:

Step 1: when the working condition is ice and snow muddy road, the mode switching control unit adopts a strong sensing mode to perform clustering analysis on relevant parameters of the ice and snow muddy road working condition, and the specific steps are as follows:

step 1.1: setting n sample objects, using x ₁ ,x ₂ ,…,x _n A representation; multi-period data acquisition is carried out during vehicle driving, and each sample object comprises m data indexes x _i1 ,x _i2 ,…,x _im I=1, 2, …, n, sample object parameterization is achieved by constructing the argument U and the data matrix X:

U＝{x ₁ ,x ₂ ,…,x _n }，

wherein x is _im M kinds of data representing the i-th sample object;

step 1.2: standard translation and extreme degradation processing are carried out on the parameterized sample object:

in the method, in the process of the invention,

mean value of k-th data in n sample objects, s _k Represents the kth number "" in n sample objects'

According to the mean square error, x _ik Non-dimensional value, x representing kth data in ith sample object _ik A calculated value representing the kth data in the ith sample object;

step 1.3: calculating the similarity degree between sample objects, and calculating the similarity degree r of the ith sample object and the jth sample object _ij ：

Sequentially calculating the similarity degree among all sample objects to form a similarity matrix R, and simplifying the similarity matrix R into a triangular matrix R ^* ：

Step 1.4: according to a triangular matrix R ^* Adopting a direct clustering method to obtain a clustering pedigree diagram;

step 1.5: presetting an initial threshold lambda, finding lambda with the best energy-saving effect through experimental design, and determining a driving working condition classification mode with the best energy-saving effect of the drive-by-wire chassis system;

step 1.6: the collected data are added into the domain U for processing, so that the real-time classification of the working conditions of the driver and the vehicle is realized;

step 1.7: for the test design in step 1.5, a plurality of different thresholds lambda are taken to represent the similarity of the same class, lambda epsilon [0,1], and the larger the lambda value is, the larger the similarity is represented:

lambda is taken out ₁ For each sample object x =1 _i By similarity class, i.e. satisfying r _ij X=1 _i And x _j Constitute the similarity class, at this time, merge r _ij Sample object of=1 is a class, resulting in λ ₁ Equivalent classification at level=1;

lambda is taken out ₂ For the next largest value, the similarity is taken directly from R to be greater than or equal to lambda ₂ Element pair (x) _i ,x _j ) Will correspond to lambda ₁ Equivalent classification of x=1 _i Class and x of the location _j Merging the classes, and merging all the classes to obtain the lambda-base ₂ Equivalent classifications of (2);

lambda is taken out ₃ For the next largest value, the similarity is taken directly from R as lambda ₃ Element pair (x) _i ,x _j ) Will correspond to lambda ₂ X in the equivalence class of (2) _i Class and x of the location _j Merging the classes, and merging all the classes to obtain the lambda-base ₃ Equivalent classifications of (2);

and so on up to lambda _n =0, where U merges into one class;

step 2: the sorting from big to small according to the cluster analysis result of the relevant parameters of the ice, snow and muddy road conditions comprises: the working conditions of the simple ice and snow muddy road surface are 0% -40%, 40% -85% and 85% -100% of the working conditions of the conventional ice and snow muddy road surface; setting environment wet coefficient omega for different ice, snow and muddy road conditions _wet ：

Step 3: according to the road condition monitor in the road condition state sensing unit, the front end acquisition signal core sensor is used for sensing the change condition of road humidity and road viscosity degree parameters in the environment, the host acquisition system is used for rapidly analyzing and processing the change condition, data are transmitted to the server through a wireless network, real-time data such as road viscosity, dry and wet conditions and the like, namely a road viscosity factor lambda and a road humidity coefficient mu are obtained, and the height of a vehicle body which needs to be reduced under different ice, snow and muddy working conditions of different vehicle types is determined according to the following formula:

wherein L is _i The wheelbase of the i-type vehicle is represented, and v represents the longitudinal speed of the vehicle;

according to the vehicle body height reduction data under the working conditions of different vehicle types, different speeds and different ice and snow muddy roads, the opening and closing of the electromagnetic valve are adjusted through the active suspension control unit to realize the inflation and deflation of the air spring and the damping of the damping-controlled continuously-adjustable shock absorber, so that the vehicle body height is adjusted.

7. The method according to claim 1, wherein the road condition sensing unit determines that the vehicle driving road condition is a ramp road surface, the ramp road surface including an uphill road surface and a downhill road surface;

when the working condition is an uphill road, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a vehicle body height sensor arranged at the front suspension of the vehicle measures the vehicle body height displacement H _uf The vehicle body height sensor arranged at the rear suspension of the automobile measures the vehicle body height displacement H _ur A vehicle body pitch angle sensor mounted at the center of mass of the vehicle body measures the actual pitch angle θ of the vehicle body _ua The theoretical pitch angle theta of the vehicle body can be calculated according to the following formula _ut ：

Wherein L is the distance between a vehicle body height sensor at the front suspension and a vehicle body height sensor at the rear suspension;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut I is less than 0.8 °, and θ _ua When the angle is larger than 3 DEG, the data theta is calculated _ua Transmitting to the electronic control unit, the active suspension control unit executes a high-gradient mode, increases the height of the rear side of the automobile chassis, reduces the height of the front side of the automobile chassis, and reaches the displacement difference delta H of the front and rear heights of the automobile body _u ＝|H _uf -H _ur The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

When the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut I is less than 0.8 °, and θ _a When the angle is smaller than 3 DEG, the data theta is calculated _ua Transmitting to the electronic control unit, the active suspension control unit executes a low-gradient mode, and only increases the height of the rear side of the chassis of the automobile until the front-rear height displacement difference delta H of the automobile body _u ＝|H _uf -H _ur The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _u ＝|θ _ua -θ _ut When the I is larger than or equal to 0.8 degrees, the electronic control unit judges that the pitch angle measurement deviation is larger, and the front and rear vehicle body height sensor data are required to be acquired again and then the vehicle is advancedComparing the pitch angle deviation of the crane body;

when the working condition is a downhill road, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a vehicle height sensor arranged at the front suspension of the vehicle measures the vehicle height displacement H _df The vehicle body height sensor arranged at the rear suspension of the automobile measures the vehicle body height displacement H _dr A vehicle body pitch angle sensor mounted at the center of mass of the vehicle body measures the actual pitch angle θ of the vehicle body _da The theoretical pitch angle theta of the vehicle body can be calculated according to the following formula _dt ：

Wherein L is the distance between a vehicle body height sensor at the front suspension and a vehicle body height sensor at the rear suspension;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt I is less than 0.8 °, and θ _da When the angle is larger than 3 DEG, the data theta is calculated _da Transmitting to the electronic control unit, the active suspension control unit executes a high-gradient mode, increases the height of the front side of the automobile chassis, reduces the height of the rear side of the automobile chassis, and reaches the displacement difference delta H of the front and rear heights of the automobile body _d ＝|H _df -H _dr The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt I is less than 0.8 °, and θ _da When the angle is smaller than 3 DEG, the data theta is calculated _da Transmitting to the electronic control unit, the active suspension control unit executes a low-gradient mode to only raise the height of the front side of the chassis of the automobile until the front-rear height displacement difference delta H of the automobile body _d ＝|H _df -H _dr The I is smaller than 4mm, and lifting of the chassis is stopped so as to keep the vehicle body horizontal;

when the pitch angle of the vehicle body deviates by delta theta _d ＝|θ _da -θ _dt When the I is larger than or equal to 0.8 degrees, the electronic control unit judges that the pitch angle measurement deviation is larger, and the front and rear vehicle body height sensor data are required to be acquired again and then the measurement is carried outAnd (5) comparing the pitch angle deviation of the vehicle body.

8. The method for controlling an active suspension of an automobile according to claim 1, wherein the road condition sensing unit determines that the running road condition of the automobile is a turning road surface;

the turning pavement comprises the following steps:

step 1: when the working condition is a turning road surface, the mode switching control unit adopts a middle sensing mode, and in the sensing data acquisition unit, a front wheel steering angle measurement system acquires the front wheel steering angle delta of the vehicle _r The vehicle speed sensor acquires the vehicle turning speed v _r When the automobile runs normally, and the lateral acceleration is not more than 0.4g and the lateral deflection angle is not more than 5 degrees, the wheel lateral deflection force can be determined according to the following formula:

wherein F is _C1 ,F _C2 ,F _C3 ,F _C4 Indicating the sideways force of each wheel on the ground when turning; k (k) _f ,k _r Representing cornering stiffness of the front axle tire and the rear axle tire; beta represents the centroid slip angle; l (L) _f ,L _r Representing the distance of the centroid to the anterior and posterior axes; omega _z Indicating the angular velocity of the automobile when the automobile rotates around the Z axis;

considering the dynamics of the Z direction and the Y direction when the automobile turns, there are:

wherein m represents the mass of the whole vehicle; i _z Indicating the angular velocity of the automobile when the automobile rotates around the Z axis; beta represents the centroid slip angle when the automobile rotates;

when the automobile turns, the load of the inner tyre is transferred to the outer wheel, and the transverse load transfer rate can be calculated according to the following formula:

wherein F is _zl ,F _zr Representing the vertical load of the left and right wheels, the sprung mass of the vehicle is not laterally displaced when ltr=0, and one wheel of the vehicle has been lifted off the ground when ltr= ±1;

step 2: in order to evaluate the rollover risk and rollover degree of an automobile during turning, a turning factor zeta is introduced, and the expression is as follows:

wherein Q is _a ,Q _b ,Q _c ,P _a ,P _b For the weighting coefficient, 0 < P _a ,P _b < 1, and P _a +P _b ＝1，0＜Q _a ,Q _b ,Q _c < 1; θ is the roll angle of the vehicle body,

is the roll angle speed of the vehicle body; a, a _y For lateral acceleration, a _yl Is critical lateral acceleration; LTR is the lateral load transfer rate, LTR _l Is critical lateral load transfer rate;

step 3: preset turning factor ζ for i-type vehicle _i The active suspension control unit executes the following strategy:

when the vehicle turns right, i.e. delta _r If the turning factor zeta is greater than the preset turning factor zeta of the i-type vehicle and is more than 0 _i When the active suspension control unit controlsThe i-type vehicle left front and left rear damping continuous adjustable shock absorber performs stretching movement, the right front and right rear damping continuous adjustable shock absorber performs compression movement, the left front and left rear air springs perform inflation, and the right front and right rear air springs perform deflation until the vehicle body is horizontal; if the turning factor zeta is smaller than or equal to the preset turning factor zeta of the i-type vehicle _i When the vehicle is in a horizontal state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do stretching motion, and the left front and left rear air springs are inflated until the vehicle body is horizontal;

when the vehicle turns left, i.e. delta _r If the turning factor zeta is less than 0 and is greater than the preset turning factor zeta of the i-type vehicle _i When the vehicle is in a state, the active suspension control unit controls the i-type vehicle left front and left rear damping continuously adjustable shock absorber to do compression motion, the right front and right rear damping continuously adjustable shock absorber to do stretching motion, the left front and left rear air springs are deflated, and the right front and right rear air springs are inflated until the vehicle body is horizontal; if the turning factor zeta is smaller than or equal to the preset turning factor zeta of the i-type vehicle _i And when the vehicle body is in a horizontal state, the active suspension control unit controls the i-type vehicle right front and right rear damping continuously adjustable shock absorber to do stretching motion, and the right front and right rear air springs are inflated.

9. The method for controlling an active suspension of an automobile according to claim 1, wherein the road condition sensing unit determines that the running road condition of the automobile is a level good road surface;

when the working condition is a level good road surface, the mode switching control unit adopts a weak perception mode, the longitudinal speed of the vehicle is obtained through a vehicle speed sensor in the sensing data acquisition unit, and the height of the vehicle body is adjusted through the active suspension control unit aiming at different vehicle types, and the method comprises the following steps:

step 1: determining the height of the vehicle body to be reduced under different vehicle speeds of different vehicle types according to the following formula:

wherein H is _i Vehicle body lowering height representing i type, L _i Representing the wheelbase of an i-type vehicle, v _i Represents the longitudinal speed eta of the i-type vehicle _i Represents the chassis protection coefficient of the i model, wherein eta is more than or equal to 0.2 _i ≤0.3；

Step 2: according to the vehicle body height reduction data under different vehicle types and different speeds, the active suspension control unit adjusts the opening and closing of the electromagnetic valve to realize the inflation and deflation of the air spring and control the damping of the damping continuously adjustable shock absorber, so that the vehicle body height is adjusted.

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